As I reported here recently ("Black Dots") some users have reported problems with the EOS 5D MkII in that there are black dots to the right of very bright point highlights. There were also some reports of vertical banding when using sRAW1.
Canon have now issued firmware 1.0.7 which they say will fix these issues. The new firmware can be downloaded from http://web.canon.jp/imaging/eosd/firm-e/eos5dmk2/firmware.html or it can be accessed via the "Downloads and Drivers" tab on the support page for the EOS 5D MkII on the Canon USA website - [LINK]
Canon specifically say that the update:
Be sure to read the instructions for the firmware update carefully. Specifically
I don't know how well the update addresses the reported problems, but I now have an EOS 5D MkII for testing and once I've managed to reproduce the original problems, I'll do a firmware update and see how well it fixes them. However from reports that I'm seeing on a number of web photography forums, it appears that the firmware update really does completely eliminate the "black dot" problem.
Canon also specifies you should update Digital Photo Professional and Picture Style Editor software along with the camera firmware. That can be done via the "Downloads and Drivers" tab on the support page for the EOS 5D MkII on the Canon USA website - [LINK]
Again, according to Canon: